Why does a low refrigerant charge cause an evaporator to ice up? June 22, 2013   Subscribe I have read that a low refrigerant charge in a refrigeration system can cause the system's evaporator to ice up. I happen to have a dehumidifier which is exhibiting this symptom. I do not expect to be able to repair the dehumidifier but, as something of an HVAC enthusiast, I am curious as to why and how this happens. I am not by any means an HVAC technician, although I would like to understand refrigeration systems better than I do now. I have a dehumidifier here which is definitely not suffering from a dirty evaporator coil or restricted airflow over the evaporator coil. It is currently operating in a room in which the temperature is 76 degrees Fahrenheit and the relative humidity is 58%. Nevertheless, the bottom part of the evaporator ices up after only a few minutes of operation: Picture of Iced Evaporator Of all the explanations I have read for why a dehumidifier's evaporator might ice over, only the "it has a slow refrigerant leak and hence a low charge" explanation seems to apply.

But I don't understand why a low refrigerant charge would result in a portion of the evaporator becoming excessively cold, and I hope someone might be able to explain it to me. For what it's worth, this dehumidifier was purchased in or around 2004, and I believe (but am not 100% sure) that it uses R-134a refrigerant. Again, I'm not looking to repair the unit. Rather, I only want to learn more about how these refrigeration systems work and what might be causing this to happen.Common Air Conditioning Problems Common Air Conditioning Problems Air conditioners can fail at any time without warning. If you live in a climate that’s as hot and humid as Atlanta’s, you are asking a lot of your air conditioner!  You probably know since living in this warm climate that any air conditioner outages can result in significant discomfort rather quickly. Many air conditioning problems are a result of insufficient maintenance.  The easiest repair is one that’s avoided altogether by keeping up on regular maintenance check-ups. 

In fact, if you haven’t been keeping up on your maintenance and notice your air conditioner starting to slack, a maintenance check-up may be just what you need to get your air conditioner back up to speed.  what is the cost of a 3 ton ac unitSome common problems homeowners experience that go beyond regular maintenance and should have checked out include: the compressor failing to turn on, the air not coming out cool enough, low airflow, and leaks.large hvac units Below are some ways you can diagnose air conditioning problems, descriptions of some common problems your air conditioning system may experience, and some special issues you should know about the refrigerant (freon) in your system.hvac system brand ratings Ways to diagnose a problem:

Check fuse box or circuit breaker.  First thing to do if your air conditioner is not functioning properly is to check the fuse box or circuit breaker that services the unit.  The fuse may need to be replaced or the circuit breaker reset. Air conditioner turns on and off frequently.  The compressor and fan controls may be worn out. Unit turning on but not cooling.  If your unit is turning on, but the air isn’t cooling efficiently, your refrigerant may be low.  You may also need to clean off the evaporator or condenser coils by brushing them off or vacuuming them.  In addition, the filter may need to be replaced.  Clogged, dirty filters block normal airflow and reduce a system’s efficiency considerably.Dirty air filters and/or closed or obstructed supply-air and return-air grilles may cause insufficient airflow through your system.These are usually associated with low refrigerant or a clogged drain pipe.  Clogs can be fixed by clearing out the clogged pipe within the evaporator coil pan. 

Leaks should always be handled by a professional HVAC contractor. Common air conditioning problems:If your air conditioner is low on refrigerant, either it was undercharged at installation or it leaks.  If it leaks, simply adding refrigerant is not a solution.  A trained AC technician should fix any leak, test the repair and then charge the system with the correct amount of refrigerant.  Remember that the performance and efficiency of your air conditioner is greatest when the refrigerant charge exactly matches the manufacturer’s specification, and is neither undercharged nor overcharged.  In addition, refrigerant leaks can be harmful to the environment.If you allow filters and air conditioning coils to become dirty, the air conditioner will not work properly, and the compressor or fans are likely to fail prematurely. Electronic Controls and Sensors Failure.  The electronic controls and sensor that cause your air conditioner, fan and condenser to kick off and on properly are often the first components to go. 

Sometimes these sensors are merely knocked out of position causing the air conditioner to cycle constantly or behave erratically.  Fortunately, problems of this nature are easy to address compared to larger mechanical failures, and won’t cost you nearly as much. Fan and Condenser Failure.  Fan and condenser failure, on the other hand, can add up to some pretty pricey repairs.  Replacing burnt-out fan motors is usually worth the expense in order to get your air conditioner up and running again, though a failed condenser can be a different story.  A new condenser is the most expensive AC repair in the books, and depending on the age and efficiency of your current air conditioner, it might be a smarter investment to just upgrade to a newer unit. Special Note About Air Conditioner Refrigerant (Freon): Contrary to popular belief, air conditioners do not consume refrigerant (freon) as a car consumes oil, so under ideal conditions it would never need changing or filling.  Therefore, a low freon level indicates a leak which should be repaired before adding more.